Reproduction activity of dairy he-goats outside the natural breeding season

摘要

Semen samples were collected regularly from dairy goats outside breeding season, to study biological diminution of reproduction activity. Semen was collected from 4 animals (3 experimental and 1 control) in January and February, and 4 animals (3 experimental animals, TA; 1 control animal, CT) from January to April every other week (TA) or monthly (CT). Additionally, semen samples were collected in weekly intervals from 3 animals during October. The sexual drive was maintained in January and February in the succeeding trial period. The volume of ejaculate and the concentration of sperm corresponded to those during the breeding season, while forward movement of sperm was below normal rate. The examination of spermatogenesis by DNA flow cytometry showed a higher total sperm cell transformation as well as a higher meiotic transformation in experimental animals compared with control animals of the same group. The testicular testosterone concentration in experimental animals increased from January to February and from January to April. However, it was lower than during the breeding season but high enough for stimulating spermatogenesis. Histomorphological results corresponded to clinical findings. Regular collection of semen outside the breeding season stimulated the proliferation of spermatogonia, thus the parenchyma remained active. The involution of the parenchyma in male goats outside the breeding season is the result of a reduced proliferation of germ cells and not of apoptosis.